Varactors and methods of manufacture and use

ABSTRACT

In an embodiment of the present invention is provided a method of manufacturing a varactor, comprising providing a substrate; positioning a bottom electrode on a surface of the substrate; placing a tunable dielectric material adjacent to and extending over the bottom electrode forming a step and in contact with a top electrode; placing an interconnect layer in contact with the bottom electrode, the tunable dielectric and the top electrode.

BACKGROUND OF THE INVENTION

Varactors are voltage tunable capacitors in which the capacitance isdependent on a voltage applied thereto. Although not limited in thisrespect, this property has applications in electrically tuning radiofrequency (RF) circuits, such as filters, phase shifters, and so on. Themost commonly used varactor is semiconductor diode varactor, which hasthe advantages of high tunability and low tuning voltage, but sufferslow Q, low power handling capability, and limited capacitance range. Anew type of varactor is a ferroelectric varactor in which thecapacitance is tuned by varying the dielectric constant of aferroelectric material by changing the bias voltage. Ferroelectricvaractors have high Q, high power handling capacity, and highcapacitance range.

One ferroelectric varactor is disclosed in U.S. Pat. No. 5,640,042entitled “Thin Film Ferroelectric Varactor” by Thomas E. Koscica et al.That patent discloses a planar ferroelectric varactor, which includes acarrier substrate layer, a high temperature superconducting metalliclayer deposited on the substrate, a lattice matching, a thin filmferroelectric layer deposited on the metallic layer, and a plurality ofmetallic conductors disposed on the ferroelectric layer and in contactwith radio frequency (RF) transmission lines in tuning devices. Anothertunable capacitor using a ferroelectric element in combination with asuperconducting element is disclosed in U.S. Pat. No. 5,721,194. Tunablevaractors that utilizes a ferroelectric layer, and various devices thatinclude such varactors are also disclosed in U.S. patent applicationSer. No. 09/419,126, now U.S. Pat. No. 6,531,936, entitled “VoltageTunable Varactors And Tunable Devices Including Such Varactors,” filedOct. 15, 1999, and assigned to the same assignee as the presentinvention.

Thus, there is strong need in the industry for an improved varactor andmethods of use and manufacture therefore.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a varactor comprising abottom electrode supported by a substrate; a tunable dielectric incontact with the bottom electrode and in contact with a top electrode;and an interconnect in contact with the top electrode and capable ofbeing in contact with a voltage source. The top electrode and thetunable dielectric may be encapsulated and the tunable dielectric layermay comprise one of: barium strontium titanate, barium calcium titanate,lead zirconium titanate, lead lanthanum zirconium titanate, leadtitanate, barium calcium zirconium titanate, sodium nitrate, KNbO.sub.3,LiNbO.sub.3, LiTaO.sub.3, PbNb.sub.2 O.sub.6, PbTa.sub.2 O.sub.6,KSr(NbO.sub.3), NaBasub.2 (NbO.sub.3).sub.5, KH.sub.2 PO.sub.4, andcomposites thereof. Further, the substrate may comprise one of: MgO,alumina (AL.sub.2 O.sub.3), LaAlO.sub.3, glass, sapphire, quartz,silicon, gallium arsenide and any material classified as low temperatureco-fired ceramic (LTCC) and the top or bottom electrode may comprise oneof: gold, aluminum, copper, nickel, palladium, platinum,platinum-rhodium, and ruthenium oxide, indium tin oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. Additionally, the left-most digit(s) of areference number identifies the drawing in which the reference numberfirst appears.

FIG. 1 depicts an embodiment of a vertical varactor of the presentinvention;

FIG. 2 illustrates, with a cross sectional and top view, a doublevaractor design of one embodiment of the present invention;

FIG. 3 is a cross sectional and top view of another embodiment of adouble varactor design using optional construction of one embodiment ofthe present invention;

FIG. 4 is another embodiment of a vertical varactor of the presentinvention;

FIG. 5 is a cross sectional and top view of the vertical varactor ofFIG. 4 encapsulated and with voltage source contacts;

FIG. 6 is a cross sectional and top view of another embodiment of avertical varactor with an interconnect providing voltage sourceconnection capability;

FIG. 7 is a cross sectional and top view of a vertical varactor of oneembodiment of the present invention with a plurality of capacitors;

FIG. 8 is a cross sectional and top view of a vertical hybrid structurevaractor of one embodiment of the present invention;

FIG. 9 is a cross sectional and top view of a mirror image verticalstructure vertical varactor in accordance with one embodiment of thepresent invention;

FIG. 10 is a cross sectional and top view of another embodiment of avaractor of the present invention; and

FIG. 11 is a cross sectional and top view of a double varactor design ofone embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, components and circuitshave not been described in detail so as not to obscure the presentinvention.

Turning now to FIG. 1, shown generally as 100, is a varactor comprising:a substrate 135, a bottom electrode 140 positioned on a surface of thesubstrate 135, a tunable dielectric material 125 positioned adjacent toand extending over the bottom electrode 140 forming a step and incontact with a top electrode 130, interconnect layers 145 and 120 may bein contact with the bottom electrode 140, the tunable dielectric 125 andthe top electrode 130. Further, an interlayer dielectric 115 may be incontact with the tunable dielectric 125, the interconnect 120 and thetop electrode 130. The interlayer dielectric 115 may be organic andphotodefinable or inorganic that is patterned, milled or etched.Although the present invention is not limited to these types ofinterlayer dielectrics nor this fabrication process. The tunabledielectric 125 may be, but is not required to be, Parascan® tunabledielectric. The term Parascan® as used herein is a trademarked termindicating a tunable dielectric material developed by the assignee ofthe present invention. Parascan® tunable dielectric materials have beendescribed in several patents. Barium strontium titanate (BaTiO3-SrTiO3),also referred to as BSTO, is used for its high dielectric constant(200-6,000) and large change in dielectric constant with applied voltage(25-75 percent with a field of 2 Volts/micron). Tunable dielectricmaterials including barium strontium titanate are disclosed in U.S. Pat.No. 5,312,790 to Sengupta, et al. entitled “Ceramic FerroelectricMaterial”; U.S. Pat. No. 5,427,988 by Sengupta, et al. entitled “CeramicFerroelectric Composite Material-BSTO—MgO”; U.S. Pat. No. 5,486,491 toSengupta, et al. entitled “Ceramic Ferroelectric CompositeMaterial—BSTO—ZrO2”; U.S. Pat. No. 5,635,434 by Sengupta, et al.entitled “Ceramic Ferroelectric Composite Material-BSTO-Magnesium BasedCompound”; U.S. Pat. No. 5,830,591 by Sengupta, et al. entitled“Multilayered Ferroelectric Composite Waveguides”; U.S. Pat. No.5,846,893 by Sengupta, et al. entitled “Thin Film FerroelectricComposites and Method of Making”; U.S. Pat. No. 5,766,697 by Sengupta,et al. entitled “Method of Making Thin Film Composites”; U.S. Pat. No.5,693,429 by Sengupta, et al. entitled “Electronically Graded MultilayerFerroelectric Composites”; U.S. Pat. No. 5,635,433 by Sengupta entitled“Ceramic Ferroelectric Composite Material BSTO—ZnO”; U.S. Pat. No.6,074,971 by Chiu et al. entitled “Ceramic Ferroelectric CompositeMaterials with Enhanced Electronic Properties BSTO Mg BasedCompound-Rare Earth Oxide”. These patents are incorporated herein byreference. The materials shown in these patents, especially BSTO—MgOcomposites, show low dielectric loss and high tunability. Tunability isdefined as the fractional change in the dielectric constant with appliedvoltage.

Barium strontium titanate of the formula BaxSr1-xTiO3 is a preferredelectronically tunable dielectric material due to its favorable tuningcharacteristics, low Curie temperatures and low microwave lossproperties. In the formula BaxSr1-xTiO3, x can be any value from 0 to 1,preferably from about 0.15 to about 0.6. More preferably, x is from 0.3to 0.6.

Other electronically tunable dielectric materials may be used partiallyor entirely in place of barium strontium titanate. An example isBaxCa1-xTiO3, where x is in a range from about 0.2 to about 0.8,preferably from about 0.4 to about 0.6. Additional electronicallytunable ferroelectrics include PbxZr1-xTiO3 (PZT) where x ranges fromabout 0.0 to about 1.0, PbxZr1-xSrTiO3 where x ranges from about 0.05 toabout 0.4, KTaxNb1-xO3 where x ranges from about 0.0 to about 1.0, leadlanthanum zirconium titanate (PLZT), PbTiO3, BaCaZrTiO3, NaNO3, KNbO3,LiNbO3, LiTaO3, PbNb2O6, PbTa2O6, KSr(NbO3) and NaBa2(NbO3)5KH2PO4, andmixtures and compositions thereof. Also, these materials can be combinedwith low loss dielectric materials, such as magnesium oxide (MgO),aluminum oxide (Al2O3), and zirconium oxide (ZrO2), and/or withadditional doping elements, such as manganese (MN), iron (Fe), andtungsten (W), or with other alkali earth metal oxides (i.e. calciumoxide, etc.), transition metal oxides, silicates, niobates, tantalates,aluminates, zirconnates, and titanates to further reduce the dielectricloss.

In addition, the following U.S. patent applications, assigned to theassignee of this application, disclose additional examples of tunabledielectric materials: U.S. application Ser. No. 09/594,837 filed Jun.15, 2000, entitled “Electronically Tunable Ceramic Materials IncludingTunable Dielectric and Metal Silicate Phases”; U.S. application Ser. No.09/768,690 filed Jan. 24, 2001, entitled “Electronically Tunable,Low-Loss Ceramic Materials Including a Tunable Dielectric Phase andMultiple Metal Oxide Phases”; U.S. application Ser. No. 09/882,605 filedJun. 15, 2001, entitled “Electronically Tunable Dielectric CompositeThick Films And Methods Of Making Same”; U.S. application Ser. No.09/834,327 filed Apr. 13, 2001, entitled “Strain-Relieved TunableDielectric Thin Films”; and U.S. Provisional Application Ser. No.60/295,046 filed Jun. 1, 2001 entitled “Tunable Dielectric CompositionsIncluding Low Loss Glass Frits”. These patent applications areincorporated herein by reference.

The tunable dielectric materials can also be combined with one or morenon-tunable dielectric materials. The non-tunable phase(s) may includeMgO, MgAl2O4, MgTiO3, Mg2SiO4, CaSiO3, MgSrZrTiO6, CaTiO3, Al2O3, SiO2and/or other metal silicates such as BaSiO3 and SrSiO3. The non-tunabledielectric phases may be any combination of the above, e.g., MgOcombined with MgTiO3, MgO combined with MgSrZrTiO6, MgO combined withMg2SiO4, MgO combined with Mg2SiO4, Mg2SiO4 combined with CaTiO3 and thelike.

Additional minor additives in amounts of from about 0.1 to about 5weight percent can be added to the composites to additionally improvethe electronic properties of the films. These minor additives includeoxides such as zirconnates, tannates, rare earths, niobates andtantalates. For example, the minor additives may include CaZrO3, BaZrO3,SrZrO3, BaSnO3, CaSnO3, MgSnO3, Bi2O3/2SnO2, Nd2O3, Pr7011, Yb2O3,Ho2O3, La2O3, MgNb2O6, SrNb2O6, BaNb2O6, MgTa2O6, BaTa2O6 and Ta2O3.

Thick films of tunable dielectric composites may comprise Ba1-xSrxTiO3,where x is from 0.3 to 0.7 in combination with at least one non-tunabledielectric phase selected from MgO, MgTiO3, MgZrO3, MgSrZrTiO6, Mg2SiO4,CaSiO3, MgAl2O4, CaTiO3, Al2O3, SiO2, BaSiO3 and SrSiO3. Thesecompositions can be BSTO and one of these components, or two or more ofthese components in quantities from 0.25 weight percent to 80 weightpercent with BSTO weight ratios of 99.75 weight percent to 20 weightpercent.

The electronically tunable materials may also include at least one metalsilicate phase. The metal silicates may include metals from Group 2A ofthe Periodic Table, i.e., Be, Mg, Ca, Sr, Ba and Ra, preferably Mg, Ca,Sr and Ba. Preferred metal silicates include Mg2SiO4, CaSiO3, BaSiO3 andSrSiO3. In addition to Group 2A metals, the present metal silicates mayinclude metals from Group 1A, i.e., Li, Na, K, Rb, Cs and Fr, preferablyLi, Na and K. For example, such metal silicates may include sodiumsilicates such as Na2SiO3 and NaSiO3-5H2O, and lithium-containingsilicates such as LiAlSiO4, Li2SiO3 and Li4SiO4. Metals from Groups 3A,4A and some transition metals of the Periodic Table may also be suitableconstituents of the metal silicate phase. Additional metal silicates mayinclude Al2Si2O7, ZrSiO4, KalSi3O8, NaAlSi3O8, CaAl2Si2O8, CaMgSi2O6,BaTiSi3O9 and Zn2SiO4. The above tunable materials can be tuned at roomtemperature by controlling an electric field that is applied across thematerials.

In addition to the electronically tunable dielectric phase, theelectronically tunable materials can include at least two additionalmetal oxide phases. The additional metal oxides may include metals fromGroup 2A of the Periodic Table, i.e., Mg, Ca, Sr, Ba, Be and Ra,preferably Mg, Ca, Sr and Ba. The additional metal oxides may alsoinclude metals from Group 1A, i.e., Li, Na, K, Rb, Cs and Fr, preferablyLi, Na and K. Metals from other Groups of the Periodic Table may also besuitable constituents of the metal oxide phases. For example, refractorymetals such as Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, Ta and W may be used.Furthermore, metals such as Al, Si Sn, Pb and Bi may be used. Inaddition, the metal oxide phases may comprise rare earth metals such asSc, Y, La, Ce, Pr, Nd and the like.

The additional metal oxides may include, for example, zirconnates,silicates, titanates, aluminates, stannates, niobates, tantalates andrare earth oxides. Preferred additional metal oxides include Mg2SiO4,MgO, CaTiO3, MgZrSrTiO6, MgTiO3, MgAl2O4, WO3, SnTiO4, ZrTiO4, CaSiO3,CaSnO3, CaWO4, CaZrO3, MgTa2O6, MgZrO3, MnO2, PbO, Bi2O3 and La2O3.Particularly preferred additional metal oxides include Mg2SiO4, MgO,CaTiO3, MgZrSrTiO6, MgTiO3, MgAl2O4, MgTa2O6 and MgZrO3.

The additional metal oxide phases are typically present in total amountsof from about 1 to about 80 weight percent of the material, preferablyfrom about 3 to about 65 weight percent, and more preferably from about5 to about 60 weight percent. In one preferred embodiment, theadditional metal oxides comprise from about 10 to about 50 total weightpercent of the material. The individual amount of each additional metaloxide may be adjusted to provide the desired properties. Where twoadditional metal oxides are used, their weight ratios may vary, forexample, from about 1:100 to about 100:1, typically from about 1:10 toabout 10:1 or from about 1:5 to about 5:1. Although metal oxides intotal amounts of from 1 to 80 weight percent are typically used, smalleradditive amounts of from 0.01 to 1 weight percent may be used for someapplications.

The additional metal oxide phases can include at least two Mg-containingcompounds. In addition to the multiple Mg-containing compounds, thematerial may optionally include Mg-free compounds, for example, oxidesof metals selected from Si, Ca, Zr, Ti, Al and/or rare earths.

The varactor of one embodiment of the present invention may provide thatany or all of the bottom electrode 140, the tunable dielectric 125, thetop electrode 130, the interconnect 120, 145 or the interlayerdielectric 115 are encapsulated. As mentioned above, an interlayerdielectric 115 may be in contact with the top electrode 130, the tunabledielectric 125 and the interconnect 120, 145.

The tunable dielectric layer may comprises one of: barium strontiumtitanate, barium calcium titanate, lead zirconium titanate, leadlanthanum zirconium titanate, lead titanate, barium calcium zirconiumtitanate, sodium nitrate, KNbO.sub.3, LiNbO.sub.3, LiTaO.sub.3,PbNb.sub.2 O.sub.6, PbTa.sub.2 O.sub.6, KSr(NbO.sub.3), NaBa.sub.2(NbO.sub.3).sub.5, KH.sub.2 PO.sub.4, and composites thereof. Further,the tunable dielectric layer may comprises a barium strontium titanate(BSTO) composite selected from the group of: BSTO—MgO, BSTO—MgAl.sub.2O.sub.4, BSTO—CaTiO.sub.3, BSTO—MgTiO.sub.3, BSTO—MgSrZrTiO.sub.6, andcombinations thereof. Further, the substrate 135 may comprise one of:MgO, alumina (AL.sub.2 O.sub.3), LaAlO.sub.3, glass, sapphire, quartz,silicon, gallium arsenide and any material classified as low temperatureco-fired ceramic (LTCC) and the top 130 or bottom 140 electrode maycomprise one of: gold, aluminum, copper, nickel, palladium, platinum,platinum-rhodium, ruthenium oxide and indium tin oxide. Theconfiguration of FIG. 1 improves on the prevention of a short and theuse of a “step over” enables ease of fabrication. In any or allembodiments of the present invention, and not limited in this respect,adhesion layers may be used between a bottom electrode and a substrate,and/or a bottomelectrode and the tunable dielectric and/or the tunabledielectric and the interlayer dielectric and/or the tunable dielectricand a top electrode or interconnect and/or a top electrode andinterconnect. Further, all electrodes may contain multi metallic layers.

Turning now to FIG. 2, another embodiment of the present invention mayprovide

at 200 a substrate 220, a plurality of bottom electrodes 215 and 225positioned on a surface of the substrate 220 separated to form a gaptherein. A tunable dielectric material 240 may be positioned on thesurface of the substrate 220 and within the gap and the tunabledielectric 240 may be at least partially overlaying the plurality ofelectrodes 215 and 225. Further, a top electrode 235 may be in contactwith the tunable dielectric 240.

The varactor of this embodiment may provide that the top electrode, thetunable dielectric and the bottom electrode are encapsulated; however,it is understood that the present invention is not limited in thisrespect. In an embodiment of the present invention, the top 235 orbottom 215 and 225 electrodes may comprise one of: gold, aluminum,copper, nickel, palladium, platinum, platinum-rhodium, and rutheniumoxide, indium tin oxide.

Turning now to FIG. 3, shown generally at 300 in a top view and 305 as across sectional view, is an embodiment of the present invention whereina varactor comprises a substrate 320; a plurality of bottom electrodes325 positioned on a surface of the substrate 320 separated to form a gaptherein. Tunable dielectric material 310 may be positioned on thesurface of the substrate 320 and within the gap. Further, thisembodiment provides that the tunable dielectric 310 may at leastpartially overlay the plurality of bottom electrodes 325. A topelectrode 335 may be in contact with the tunable dielectric 310 and aplurality of interconnects 315 and 330 may be on a surface of theplurality of electrodes 325 enabling a connection to a voltage source.

Although not limited in this respect, an embodiment of the presentinvention may provide that the top electrode, the tunable dielectric andthe bottom electrode be encapsulated. Further, the top or bottomelectrode may comprise one of: gold, aluminum, copper, nickel,palladium, platinum, platinum-rhodium, and ruthenium oxide, indium tinoxide.

Turning now to FIG. 4, as depicted generally at 400, is a varactorcomprising a substrate 420 and a first electrode 415 positioned on asurface of the substrate 420 and a second electrode 425 positioned onthe surface of the substrate forming a gap 430 between the first 415 andsecond 425 electrodes. A tunable dielectric material 410, such asParascan®, is positioned on the surface of the substrate 420 and withinthe gap. Although not limited in this respect, an embodiment of thepresent invention may provide that the varactor 400 may be encapsulatedwith a dielectric layer as shown in more detail in FIG. 5. Theelectrodes in this embodiment of the present invention are capable ofbeing multi-layered with multiple metals. The multi-layered metals maybe the same metals per layer or different. Further, the structure ofFIG. 4 enables the electrodes to be different sizes and permits the useof small electrodes.

As mentioned above, the tunable dielectric layer may comprises one of:barium strontium titanate, barium calcium titanate, lead zirconiumtitanate, lead lanthanum zirconium titanate, lead titanate, bariumcalcium zirconium titanate, sodium nitrate, KNbO.sub.3, LiNbO.sub.3,LiTaO.sub.3, PbNb.sub.2 O.sub.6, PbTa.sub.2 O.sub.6, KSr(NbO.sub.3),NaBa.sub.2 (NbO.sub.3).sub.5, KH.sub.2 PO.sub.4, and composites thereof;or the tunable dielectric layer may comprise a barium strontium titanate(BSTO) composite selected from the group of: BSTO—MgO, BSTO—MgAl.sub.2O.sub.4, BSTO—CaTiO.sub.3, BSTO—MgTiO.sub.3, BSTO—MgSrZrTiO.sub.6, andcombinations thereof.

Also, the substrate may comprise one of: MgO, alumina (AL.sub.2O.sub.3), LaAlO.sub.3, glass, sapphire, quartz, silicon, galliumarsenide and any material classified as low temperature co-fired ceramic(LTCC) and the first or second electrode may comprise one of: gold,aluminum, copper, nickel, palladium, platinum, platinum-rhodium,ruthenium oxide and indium tin oxide.

FIG. 5 more clearly depicts, with a top view at 500 and cross sectionalview at 505, the encapsulation of the varactor of FIG. 4 with substrate520, electrodes 525 and 540, tunable dielectric 510 being at leastpartially encapsulated 535. Further, the contact points 545 and 550 maybe connected to a voltage source via an interconnect through theencapsulation material. This arrangement eases fabrication and mayprovide two or more capacitors.

Turning now to FIG. 6 is shown a top view 600 and cross sectional view605 of an embodiment of the present invention of a varactor, comprisinga bottom electrode 625 supported by a substrate 620. The bottomelectrode 625 of this embodiment of the present invention may be in aninterdigitated form. A tunable dielectric 610, such as, but not limitedto, Parascan®, may be in contact with the bottom electrode 625 and incontact with a top electrode 615. The top electrode 615 may also be incontact with an interconnect 640 and capable of being in contact with avoltage source. This arrangement may facilitate the voltage sourcecontact by the varactor while maintaining the desired width of the gap,desired top electrode size and desired thickness of tunable dielectric.The gap thickness may be placed close enough to create the desiredtuning.

Further, in an embodiment of the present invention, but not limited inthis respect, the top electrode 615 and the tunable dielectric 610 maybe encapsulated. Again, and not limited in this respect, the tunabledielectric layer may comprises one of: barium strontium titanate, bariumcalcium titanate, lead zirconium titanate, lead lanthanum zirconiumtitanate, lead titanate, barium calcium zirconium titanate, sodiumnitrate, KNbO.sub.3, LiNbO.sub.3, LiTaO.sub.3, PbNb.sub.2 O.sub.6,PbTa.sub.2 O.sub.6, KSr(NbO.sub.3), NaBasub.2 (NbO.sub.3).sub.5,KH.sub.2 PO.sub.4, and composites thereof or the tunable dielectriclayer may comprise a barium strontium titanate (BSTO) composite selectedfrom the group of: BSTO—MgO, BSTO—MgAl.sub.2 O.sub.4, BSTO—CaTiO.sub.3,BSTO—MgTiO.sub.3, BSTO—MgSrZrTiO.sub.6, and combinations thereof.Further, the substrate 620 may comprise one of: MgO, alumina (AL.sub.2O.sub.3), LaAlO.sub.3, glass, sapphire, quartz, silicon, galliumarsenide and any material classified as low temperature co-fired ceramic(LTCC) and the top 615 or bottom 625 electrode may comprise one of:gold, aluminum, copper, nickel, palladium, platinum, platinum-rhodium,and ruthenium oxide, indium tin oxide.

Turning now to FIG. 7, shown as a top view at 700 and cross section viewat 705 is an embodiment of the present invention wherein a varactor 705may comprise: a bottom electrode 740 supported by a substrate 730 and afirst tunable dielectric 715 may be in contact with the bottom electrode740 and in contact with a first top electrode 720. A second tunabledielectric 735 may be in contact with the bottom electrode 740 and incontact with a second top electrode 725. A first interconnect 710 may bein contact with the first top electrode 720 and a second interconnect750 may be in contact with the second top electrode 725, the first andsecond interconnects 710 and 750 may be capable of being in contact witha voltage source.

An embodiment of the present invention, although not limited in thisrespect provides that the first 720 and second 725 top electrodes andsaid first 715 and second 735 tunable dielectrics may be encapsulated.Further, in an embodiment of the present invention, the top 720 and 725or bottom 740 electrodes may comprise one of: gold, aluminum, copper,nickel, palladium, platinum, platinum-rhodium, ruthenium oxide andindium tin oxide.

Turning now to FIG. 8, shown as a top view at 800 and cross section(through dotted line 890) view at 805 is an embodiment of the presentinvention wherein is provided a varactor comprising a substrate 835 anda plurality of bottom electrodes 825 positioned on a surface of thesubstrate 835 separated to form a gap therein. A tunable dielectricmaterial 840 may be positioned on the surface of the substrate 835 andwithin the gap, the tunable dielectric 840 may partially overlay theplurality of bottom electrodes 825 and the top electrode 830 may be incontact with the tunable dielectric 840. Interconnect layers 810 and 815may be in contact with at least a portion one of the plurality of bottomelectrodes 825 and portion of the top electrode 830, and a portion ofthe tunable dielectric 840.

In an embodiment of the present invention and not limited in thisrespect the varactor may further comprise an interlayer dielectric 855capable of being in contact with the tunable dielectric 840. Further, inan embodiment of the present invention, at least a portion of the topelectrode 830, the tunable dielectric 840, the interlayer dielectric 855and the interconnects 810 and 815 are capable of being encapsulated asshown at 850. The top or bottom electrode may comprise one of: gold,aluminum, copper, nickel, palladium, platinum, platinum-rhodium, andruthenium oxide, indium tin oxide.

Turning now to FIG. 9 another embodiment of the present inventionprovides, as shown in a top view at 900 and cross section view at 905(through dotted line 990), a varactor comprising a substrate 930; aplurality of bottom electrodes 925 and 950 positioned on a surface ofthe substrate 930 separated to form a gap therebetween. A tunabledielectric material 945 may be positioned on the surface of thesubstrate 930 and within the gap, the tunable dielectric 945 maypartially overlay the plurality of electrodes 925 and 950 and aplurality of top electrodes 935 and 940 may be in contact with thetunable dielectric 945. Interconnect layer 915 may be in contact with atleast a portion one of the plurality of bottom electrodes 925 and 950and portion of the plurality of top electrodes 935 and 940, and aportion of the tunable dielectric 945. In an embodiment of the presentinvention and not limited in this respect, the plurality of topelectrodes 935 and 940 may be between a plurality of interlayerdielectric 955 and at least a portion of the plurality of top electrodes935 and 940, said tunable dielectric 945, the plurality of interlayerdielectric 955 and the interconnect 915 are capable of beingencapsulated.

Although not limited in this respect, the top 935 and 940 or bottom 925and 950 electrodes may comprise one of: gold, aluminum, copper, nickel,palladium, platinum, platinum-rhodium, and ruthenium oxide, indium tinoxide.

Turning now to FIG. 10 another embodiment of the present inventionprovides, as shown in a top view at 1000 and cross section view at 1005(crossed at dotted line 1090), a varactor comprising a substrate 1035; aplurality of bottom electrodes 1015 and 1040 positioned on a surface ofthe substrate 1035 separated to form a gap between the plurality ofbottom electrodes 1015 and 1040. A tunable dielectric material 1030positioned on the surface of the substrate 1035 and within the gap maypartially overlay the plurality of bottom electrodes 1015 and 1040 and aplurality of top electrodes 1020 and 1025 may be in contact with thetunable dielectric 1030. An interconnect layer 1010 and 1050 may be incontact with at least a portion one of the plurality of bottomelectrodes 1015 and 1040 and portion of the plurality of top electrode1020 and 1025, and a portion of the tunable dielectric 1030.

In one embodiment of the present invention and not limited in thisrespect, the plurality of top electrodes 1020 and 1025 may be separatedby an interlayer dielectric and at least a portion of the plurality oftop electrodes 1020 and 1025, the tunable dielectric 1030, the pluralityof interlayer dielectrics 1060 and the interconnect 1010 and 1050 arecapable of being encapsulated as depicted at 1055.

FIG. 11 as shown as a top view at 1100 and cross section view at 1105provides a varactor comprising a substrate 1125, a bottom electrode 1145positioned on a surface of the substrate 1125; a first tunabledielectric portion 1120 in contact with a first side of the bottomelectrode 1145 and a portion of the substrate 1125; a second tunabledielectric portion 1150 in contact with a second side of the bottomelectrode 1145 and a portion of the substrate 1125; a first interconnect1110 in contact with a first side of the tunable dielectric 1120 and incontact with a first top electrode 1130 and a portion of the substrate1125; and a second interconnect 1110 in contact with a second side ofthe tunable dielectric 1150 and in contact with a second top electrode1155 and a portion of the substrate 1125. Although not limited in thisrespect the first and second top electrodes 1130 and 1155 form a gapthere between and are capable of connecting to a voltage source.Further, again not limited in this respect, at least a portion of thevaractor may be encapsulated 1140 and the first or second top 1130 and1155 or bottom electrodes 1145 may comprise one of: gold, aluminum,copper, nickel, palladium, platinum, platinum-rhodium, and rutheniumoxide, indium tin oxide.

In yet another embodiment of the present invention, a varactor maycomprise at least one bottom electrode supported by a substrate; atleast one top electrode with a tunable dielectric separating the atleast one bottom and at least one top electrode; and an interconnectlayer in contact with at least a portion one of at least one bottomelectrode and portion of the at least one top electrode, and a portionof the tunable dielectric. Further, an interlayer dielectric may be incontact with any or all of the at least one bottom electrode, the atleast one top electrode and the tunable dielectric and any or all of theat least one bottom electrode, the at least one top electrode and thetunable dielectric may be encapsulated. Although the present inventionis not limited in this respect.

In another embodiment of the present invention is provided a method ofmanufacturing a varactor, comprising: providing a substrate; positioninga bottom electrode on a surface of the substrate; placing a tunabledielectric material adjacent to and extending over the bottom electrodeforming a step and in contact with a top electrode; placing aninterconnect layer in contact with the bottom electrode, the tunabledielectric and the top electrode. The method may further compriseencapsulating any or all of the bottom electrode, the tunabledielectric, the top electrode, the bottom electrode or the interlayerdielectric. The method may also further comprise placing an interlayerdielectric in contact with the top electrode, the tunable dielectric andthe interlayer dielectric and the top or bottom electrode may compriseone of: gold, aluminum, copper, nickel, palladium, platinum,platinum-rhodium, and ruthenium oxide, indium tin oxide.

Another method of manufacturing a varactor, may comprise: providing asubstrate; positioning a plurality of bottom electrodes on a surface ofthe substrate separated to form a gap therein; positioning a tunabledielectric material on the surface of the substrate and within the gap,the tunable dielectric at least partially overlaying the plurality ofelectrodes; and placing a top electrode in contact with the tunabledielectric. This embodiment may further comprise encapsulating the topelectrode, the tunable dielectric and the bottom electrode.

While the present invention has been described in terms of what are atpresent believed to be its preferred embodiments, those skilled in theart will recognize that various modifications to the discloseembodiments can be made without departing from the scope of theinvention as defined by the following claims.

1. A method of manufacturing a varactor, comprising: providing asubstrate; positioning a bottom electrode on a surface of the substrate;placing a tunable dielectric material adjacent to and extending oversaid bottom electrode forming a step and in contact with a topelectrode; placing an interconnect layer in contact with said bottomelectrode, said tunable dielectric and said top electrode.
 2. The methodof claim 1, further comprising encapsulating any or all of said bottomelectrode, said tunable dielectric, said top electrode, said bottomelectrode or said interlayer dielectric.
 3. The method of claim 1,further comprising placing an interlayer dielectric in contact with saidtop electrode, said tunable dielectric and said interlayer dielectric.4. The method of claim 3, wherein said top or bottom electrode comprisesone of: gold, aluminum, copper, nickel, palladium, platinum,platinum-rhodium, and ruthenium oxide, indium tin oxide.
 5. A method ofmanufacturing a varactor, comprising: providing a substrate; positioninga plurality of bottom electrodes on a surface of the substrate separatedto form a gap therein; positioning a tunable dielectric material on thesurface of the substrate and within said gap, said tunable dielectric atleast partially overlaying said plurality of electrodes; and placing atop electrode in contact with said tunable dielectric.
 6. The method ofclaim 5, further comprising encapsulating said top electrode, saidtunable dielectric and said bottom electrode.
 7. The method of claim 5,wherein said top or bottom electrode comprises one of: gold, aluminum,copper, nickel, palladium, platinum, platinum-rhodium, and rutheniumoxide, indium tin oxide.